Peer to peer communications may occur between a variety of different peer to peer communications devices. Access terminals, e.g., mobile wireless devices, may operate as communications peers in a peer to peer system. Access routers, e.g., base stations which support peer to peer communications and which may also support one or more other, e.g., non-peer to peer communications technologies, may also act as communications peers. Access routers may be supplied with power via wired land lines and thus may have far more available power than access terminals which may be limited by the amount of power that can be supplied, e.g., by a battery which can be held in a person's hand. Some access routers routinely transmit pilots which can be detected and used by device's within the access router's coverage area to generate channel estimates. In some systems these pilots are transmitted on a pilot channel or other control channel and are transmitted irrespective of whether or not traffic data is being transmitted or is waiting to be transmitted. Power consumption by such routine transmissions is normally not a concern since the access router is normally not constrained by battery power limitations
Communications systems often include far fewer access routers than access terminals. This is due in part to the fact that access routers are often designed to support communications with multiple access terminals simultaneously. Thus, in such embodiments, access routers may be expected to interact and/or communicate with a large number of access terminals at any given time.
Access terminals which are operating in peer to peer mode may not be communicating signals to an access router on a regular basis if at all. To facilitate channel estimation, prior to transmitting traffic data, a peer communications device may transmit one or more pilots to the peer device which is to receive traffic data. However, in the absence of traffic data to transmit, no pilots may be transmitted.
Given that pilots may not be transmitted by wireless terminals that do not have data to transmit, it may be difficult for an access router to maintain a current estimate of a communications channel between the access router and the wireless terminal. Furthermore, while the access terminal may be able to communicate interactively with a large number of devices, there may still be a far larger number of devices within the coverage area of the access router that are not actively communicating with the access router at a given point in time. Thus, while the access router may have sufficient signals from access terminals with which it is actively communicating traffic data to produce channel estimates, the access router may not have sufficient reliable data to generate channel estimates for all peer to peer communications devices in its coverage area, in part due to the fact that some peer to peer devices may not transmit pilots on a regular basis. In addition, requiring an access router to maintain channel estimates for all access terminals in the access router's coverage area, regardless of their level of communications activity, may place an excessive burden on the access router.
In the case of some peer to peer systems, a receiving device normally generates a channel estimate from signals, e.g., pilot signals, received from a peer to peer device immediately prior to or during traffic data transmission from the transmitting peer device to the receiving peer device. In such systems, the receiving device normally uses a channel estimate generated from the received pilots to correct for distortions introduced into the signal by the communications channel. Such an approach may not be particularly well suited for low data rate transmissions since the pilots may represent an excessive amount of overhead relative to the amount of information being communicated.
It would be advantageous if new methods and/or apparatus could be developed in a peer to peer system which could be used to take advantage of pilot signals routinely transmitted by access routers but that would not require a similar transmission of pilot signals by non-access router peer devices. In addition, it would be desirable if one or more of the new methods or apparatus would allow for communication with an access router using peer to peer signaling without requiring the access router to generate a channel estimate to successfully receive and recover information transmitted to the access router.